Rent Shop Volunteer Join

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
1 rating

Monday - April 13, 2009

From: Leander, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Fronds turning brown on yucca in Leander, TX
Answered by: Barbara Medford

QUESTION:

Dear Mr. Smarty Plants, I live Northwest of Austin in Leander and have grown a spanish dagger yucca for several years. It is 8 feet tall and each spring it puts up a showy spike of blooms. The old fronds are turning brown, the new green ones have brown on them and the trunk is beginning to lean. Now there are 8 or so pups beginning to sprout. There are icky yucca bugs on all of the surrounding yuccas which we are treating with pyrethrins. I have not watered this xeric part of our garden much in the past year so this could be a contributing factor. Can I save our beautiful plant and if so how? We could cut it down and let the pups grow but it is such a beautiful centerpiece. How can we save it?

ANSWER:

There are two plants in our Native Plant Database that have "Spanish Dagger" as one of their common names: Yucca aloifolia (aloe yucca) which is not native to Texas, and referred to as Spanish Bayonet  in this Floridata website; the other is Yucca treculeana (Don Quixote's lace) is shown as growing only in Texas. It probably doesn't much matter which you have, both are adaptable to the conditions around Austin and Leander.

Because we are not plant pathologists, we really don't know what is causing the problems your yucca is encountering. However, we found a website from the University of Florida Research Education Center, Yucca Production Guide, which gave very complete information on insect pests and diseases as well as instructions for care and propagation.  Generally speaking, yuccas are not considered to be seriously threatened by most of these problems. We aren't entomologists, either, but we did feel we should check out "icky yucca bugs". We learned that there really is a bug named the "yucca bug" (they omitted the "icky") and we found a site from the Bug Guide with pictures and some discussion of Halticoma valida. It has some pictures and you're right, it's one ugly bug. We're a little concerned about your spraying pyrethrins on the other plants. Is it possible that what you are seeing are the larvae of the yucca moth? The yucca and the yucca moth are co-dependant, in that the yucca moth is the sole pollinator of the yucca, and the yucca moth needs the seeds of the yucca for the larvae to feed on. 

In terms of saving the big centerpiece yucca, although they are ordinarily long-lived plants, this one may have reached the end of its life cycle. The spots may be from mealy bugs or one of the other less fearsome bugs discussed in the article from the Florida Research Education Center, and are likely not a serious threat. Browning lower leaves are a common sight on yucca, and the leaves can just be peeled off (very carefully). Don't try to overwater, this is a desert plant, and certainly don't water from above, as in sprinklers. One of the diseases mentioned in the article on Yucca was fungal in nature, and excess water, especially from above, contributes to that. The yucca is a very tough survivor plant; even if you cut it down, it will put new sprouts up from pieces of root. Keep fallen leaves and other trash cleaned up around the base and watch it for a while, it could bounce back, and if it doesn't, you have spares. 


Yucca treculeana

Yucca treculeana

Yucca treculeana

Yucca treculeana

 

 

More Diseases and Disorders Questions

Treating cuts in tree trunks
November 21, 2009 - We have two young trees that deer made bad cuts in the trunks. What can we put on cuts to keep bugs and disease from getting in them.? Thank you.
view the full question and answer

Long term effects of pesticide from Lubbock TX
March 20, 2013 - I have 9 western pecan trees about 20 years old. Trunk sizes is from 18" to 39". I used a product Bayer Tree and Shrub, applied to the trees. I wonder what it will do to the trees. I talkd to Bayer ...
view the full question and answer

Bark damage to Tulip Tree
August 10, 2006 - I have a tulip tree planted. It is about 9-10 years old. Two years ago the tree looked as though the trunk was cracked. Maybe hit by lightning after a storm. This year the bark on the side of tree...
view the full question and answer

Problems with giant coneflower in Richardson TX
June 05, 2010 - Dear Mr Smarty Plants- I have had a giant coneflower in my garden for 2 years now. This year it came up like it always had..got lots of leaves and then withered..turned brown and died. It got plent...
view the full question and answer

Problems with dogwood tree in Jacksonville FL
February 28, 2010 - Sir, I believe I have a Cornus drummondii, a stiff dogwood tree on my lawn which a few years ago was big, lush and full of branches and leaves. In the last 2 years I have noticed about 80% of it drop...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.